Over time, the internal membrane switch or contact points for the "Mode" button can wear out or become corroded, making it unresponsive.
The Tronic T4X is a $30–$50 device. If you have tried everything: tronic t4x stuck on standby
Briefly connect the flat battery to a non-smart "dumb" charger for 15–30 minutes to raise the base voltage above the T4X detection threshold. 3. Inspect and Clean the Mode Button Over time, the internal membrane switch or contact